1. Field of the Invention
The present invention relates to a screw for fixing vertebra, and more specifically, to a screw for fixing vertebra for giving various option, for screw insertion, to an operator with maintaining condition of lower profile screw.
2. Description of the Related Art
In general, spinal diseases include prolapsed intervertebral disk (spinal disk) and spinal scoliosis, and a patient with part of the spine damaged cannot engage in activities necessary for daily life in such a condition. Even if the extent of damage is not so serious, if the damaged part of the spine is pressed or touched by another adjacent part it may cause pain. Due to uneven division of various loads applied to the human body, pain is induced or a degenerative disease is brought about.
Therefore, a patient with part of the spine broken or damaged cannot lead a stable daily life unless the damaged part is corrected by carrying out a surgery for supporting it by using an artificial aid in the damaged part.
Of such spinal diseases, spinal scoliosis is a disease in which vertebrae are bent and twisted. If the spinal scoliosis is left alone, deformation of the spine progresses to eventually bring about serious deformity, followed by complications such as deformation of internal organs.
Such spinal scoliosis can be cured completely by wearing a brace or surgery according to the bent angle of vertebrae. In the methods of operating on spinal scoliosis, there is a method known as a pedicle screw inserting technique for correcting by inserting screws into bent vertebrae.
The pedicle screw inserting technique is a method for helping the spine recover to a normal condition by inserting pedicle screws into bent vertebrae and connecting the pedicle screws with each other using a rod.
However, in the case of screws for fixing vertebra used in the conventional pedicle screw insertion surgery, the degree of freedom between the screw body driven into and fixed to the vertebra and the fastening screw for fixing the connecting rod is so low that it is not possible to move in a desired angle range. Therefore, there is a problem that it is difficult for the operator to perform a fixing operation within a desired range early during an operation and after performing the pedicle screw insertion surgery there are considerable constraints for the patient to perform spinal motion.